The Nord Lead or Nord Rack may be the thing for you too. I own a Nord Rack
and it has all the knobs you can ask for, MIDI, and 12-voice polyphony (when
you install the card), which is important if you want to make other textures
besides filter sweeping acid lines. I think it's a pretty good machine, but
it doesn't quite live up to the hype - Bass tones are really tough to make fat
and the higher frequencies sometimes come out a little thin and metallic. The
user interface is great though and in fact can even wind up being a useful
learning tool - I learned a lot about envelopes, waveforms/oscillators,
filters, etc. by reading the manual and taking pains to listen to how each
knob affects a sound. The arpeggiator is pretty good and there are a whole
host of MIDI functions (Oscillator sync to MIDI clock, fantastic & intuitive
SysEx patch dumping capability - don't buy the PCI card) that make it a great
machine. I just wish it was a little fatter. My best results have come by
sampling it and then freaking the samples with some more DSP.
I also listened to the JP8000 briefly in the store and it seemed super nice.
I haven't heard the Yamaha machines.
There's also another digital analog machine called the Rave-o-lution 909 which
has a lot of knobs but I've never seen it in a store or heard it.
Finally, I highly agree with the point about forgetting GM - GM is about
developing a standard set of sounds that make the transfer of music between
systems and artists easy - analogue synths are best used to create sounds that
are highly unique -
Jay B